Of North Dakota's 318,190 households, 18,492 households had more than $1 million or more in investable assets in 2015, according to an analysis by Phoenix Marketing International. That translates into a ratio of millionaires to total households of 5.81 percent.

Between 2012 and 2015, the Peace Garden State leapt an astounding 25 spots to 18th in the country, largely thanks to the oil boom of the 2000's and 2010's

That boom is slowing down, so it'll be next year before we see the full affect of the decline on the state's ranking.

In comparison, our neighbor Minnesota ranked 11th in the nation, with 6% of households claiming a million or more in assets.

At the top of the list is Maine, at 7.7%; last is Mississippi, at just 3.94%, compared to the national average of 5.37%.